[gi] fix try except blocks so they work in Python 2.5
[gi] fix try except blocks so they work in Python 2.5

* use etype, e = sys.exc_info[:2] to extract error details instead of
  except Exception as e or except Exception, e

Distrotech/pygobject,Distrotech/pygobject,Distrotech/pygobject,Distrotech/pygobject